OnionShare lets you securely and anonymously share files of any size. It works by starting a web server, making it accessible as a Tor onion service, and generating an unguessable URL to access and download the files. It doesn't require setting up a server on the internet somewhere or using a third party filesharing service. You host the file on your own computer and use a Tor onion service to make it temporarily accessible over the internet. The other user just needs to use Tor Browser to download the file from you.

用法的部份就更清楚了：

Open OnionShare, drag and drop files and folders you wish to share into it, and click Start Sharing. After a moment, it will show you a .onion URL such as http://asxmi4q6i7pajg2b.onion/egg-cain. This is the secret URL that can be used to download the file you're sharing.